1. Field of the Invention
The present invention relates to a system for controlling a gear shift of a transmission in a hybrid vehicle which is provided with an electric motor in addition to an internal combustion engine or the like as a prime mover, and more specifically, to a shift control system intended for the hybrid vehicle which is constructed to transmit a motive energy of the motor to a wheel when a gear shift is executed.
2. Related Art
In the vehicle, which is provided with a clutch and a transmission between an engine and wheels, a control for lowering a torque capacity of a clutch at a shifting time of the transmission is known in the prior art. When the torque capacity of the clutch is thus lowered at the shifting time of the transmission, however, there is a problem such that a driving torque or an acceleration is fluctuated due to lowering of the torque to be transmitted to the wheels. In this connection, a technology which is capable of suppress the lowering of the torque or the acceleration even if the torque capacity of the clutch is lowered at the shifting time of the transmission is known, and one example of such technology is disclosed in Japanese Patent Laid-Open No. 11-141665.
According to the vehicle as disclosed in Japanese Patent Laid-Open No. 11-141665, it is constructed to transmit a motive energy of the engine to the transmission through the clutch. The transmission has an input shaft and an output shaft, and the input shaft is connected to the clutch and the output shaft is connected to the wheel through differential gears. Also, a motor is connected to the input shaft or the output shaft. Moreover, it is constructed to supply an electric power of a battery to the motor through a controller. The clutch is released at the shifting time of the transmission and the output shaft is driven by supplying an electric current to the motor, thereby to maintain the acceleration feeling. Besides, a technology for transmitting the motive energy of the motor to the wheel when the clutch is released is also disclosed in Japanese Patent Laid-Open No. 2002-89594, other than aforementioned Japanese Patent Laid-Open No. 11-141665.
However, there is a problem such that an electric power source such as a battery for supplying the electric power to the motor has to grow in its capacity and in its size, if the control takes place to compensate the lowering of the torque to be transmitted to the wheels with an output torque of the motor by means of driving the motor with the electric power of the battery when the clutch is released, as disclosed in Japanese Patent Laid-Open No. 11-141665.